Yes, they are. Worse, I’ve seen them shrink down to nothing in the face of congestion with TCP traffic. If Quic is indeed the future protocol, it’s a good thing to move it into the kernel IMO. It’s just madness to provide these massive userspace impls everywhere, on a packet switched protocol nonetheless, and expect it to beat good old TCP. Wouldn’t surprise me if we need optimizations all the way down to the NIC layer, and maybe even middleboxes. Oh and I haven’t even mentioned the CPU cost of UDP.

OTOH, TCP is like a quiet guy at the gym who always wears baggy clothes but does 4 plates on the bench when nobody is looking. Don't underestimate. I wasted months to learn that lesson.